package 重排字符串;

import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        char[] ch = in.next().toCharArray();
        int[] st = new int[26];
        char[] res = new char[n];
        int cnt = 0;
        char t = '0';
        for (int i = 0; i < n; i++) {
            if (++st[ch[i]-'a'] > cnt) {
                cnt = st[ch[i]-'a'];
                t = ch[i];
            }
        }
        if (cnt > (n + 1 )/2) {
            System.out.println("no");
        } else {
            System.out.println("yes");
            int i = 0;
            while (st[t - 'a']-- > 0) {
                res[i] = t;
                i += 2;
            }
            for (int j = 0; j < 26; j++) {
                if (st[j] <= 0) {
                    continue;
                }
                char tmp = (char) (j + 'a');
                while (st[j]-- > 0) {
                    if (i >= n) {
                        i = 1;
                    }
                    res[i] = tmp;
                    i += 2;
                }
            }
            for (int j = 0; j < n; j++) {
                System.out.print(res[j]);
            }
        }
    }
}
